Possible Clues:

• 2003 #1 hit for OutKast
• OutKast hit that asks, "What's cooler than being cool?"
• 2003-'04 OutKast chart-topper
• Outkast hit single
• 2003 #1 Outkast hit
• 2003 Outkast hit whose title is a casual greeting
• Slangy welcome
• #1 hit for OutKast
• OutKast classic
• 2004 #1 hit for OutKast